Wireless communication devices typically feature a transmitter chip that drives an antenna. The antenna may be integrated inside the transmitter chip, but more commonly the transmitter chip and the antenna are integrated onto a module or other device.
Lower frequencies with longer wavelengths have a larger near-field region than do higher frequency signals. Thus radio waves commonly used with Radio-Frequency Identification (RFID) have a near-field region of about a few meters, but the data rates are limited by the radio frequency to perhaps several kHz to a few MHz. Thus RFID systems tend to transmit small amounts of data, such as identifier data.
It is desired to wirelessly transmit video and other data that require high data rates. RFID is too limited by the low frequency of radio waves. The assignee has developed wireless communication systems that use Extremely High-Frequency (EHF) electromagnetic radiation rather than using Radio-Frequency (RF) electromagnetic radiation. EHF radiation has a frequency in the range of 30 GHz to 300 GHz. This higher frequency allows for data rates as much as 1,000 times faster than with RF. However, the wavelength of radiation is much smaller than for RF. The smaller EHF wavelength reduces the near-field envelope to perhaps 1 or 2 centimeters.
The related application by the inventors, U.S. Ser. No. 61/799,605, shows placement of multiple EHF devices on a common substrate in order to isolate radiation from one device to a neighboring device and to establish a common PCB structure to define end product characteristics, such as working distance and crosstalk between devices. The use of structures within the substrate and surrounding the substrate allows for redirection of electromagnetic radiation. Electromagnetic radiation emitted from a transducer (with transmission and/or reception properties similar to an antenna but realizable with multiple physical configurations) may be directed upward by such structures to allow a receiver to be placed above the transmitter. This is known as vertical launch of the electromagnetic radiation. Alternatively, electromagnetic radiation from the transmitting transducer may be directed sideways by such structures to allow a receiver to be placed beside the transmitter. This is known as edge launch of the electromagnetic radiation. Electromagnetic radiation from the transmitting transducer also may be directed parallel to a substrate or perpendicularly to a substrate.
While the substrate structures are useful in redirecting electromagnetic radiation from a single transmitter to a single receiver, it is also desired to have multiple transmitters on a same device or substrate structure. For example, the signaling bandwidth of a single transmitter-receiver pair may be less than a desired bandwidth. Having two transmitter-receiver pairs may double the available bandwidth, while having four transmitter-receiver pairs may quadruple the available bandwidth.
Therefore, it is sometimes desired to have multiple transmitters and receivers on each mated device. For example, a tablet computing device may have two transmitters and two receivers, which communicate with two receivers and two transmitters on a dock or base-station device when in close proximity. However, the envelopes of electromagnetic radiation from the multiple transmitters may superimpose on each other, potentially causing interference, cross-talk, standing waves, nodes, nulls, and/or other phenomena. This interference may lead to impaired signal integrity and reception at the receivers, and erratic carrier waves and signaling.
When the mated devices are not exactly in alignment with each other, the interference phenomena may vary with the amount of mis-alignment of the two mated devices. The amount of signal degradation may vary with position and alignment. Since the size of the electromagnetic radiation envelopes may be quite small, such as 1-2 cm or less, and nodes caused by two or more interfering envelopes may be spaced only a millimeter or so apart, a small misalignment of only a few millimeters may cause drastic changes in signal strength. The receiving transducer may be moved from a maxima within the interfering envelopes to a minima node within the envelopes by a slight repositioning. This sensitivity to misalignment is undesirable.
What is desired is a close-proximity communication device that is tolerant to mis-alignment with a mated device. A close-proximity communication device having substrate structures to reflect, absorb, or direct electromagnetic radiation is desirable to prevent or reduce multi-path interference from superposition of multiple electromagnetic radiation envelopes emitted from multiple transmitters that are close to one another. Structures to isolate one transmitter's electromagnetic radiation envelope from the electromagnetic radiation envelope of another transmitter are desirable.